Run as non-root user

[olevski]

After trying a few things it seems that this image cannot be run as non-root without rebuilding it.

Would you accept a PR to make it so that a non-root user (i.e. userid and groupid != 0) runs jena?

If this is possible with the current image (without rebuilding it) it would be much appreciated if you can let me know how to do it.

[namedgraph]

This image runs as non-root: https://github.com/AtomGraph/fuseki-docker